The invention relates to improvements in methods of making recesses in at least partially metallic workpieces. More particularly, the invention relates to improvements in methods of making recesses (e.g., in the form of tapped or untapped blind holes or through holes) in workpieces which can be used in torque transmitting. apparatus, for example, in the housings or covers of friction clutches for use in motor vehicles.
As a rule, a recess in a metallic workpiece is obtained by removing material from the workpiece, e.g., by resorting to a drill or to another suitable material removing tool. If the workpiece is to be provided with an internal thread, the treatment with a drill or with another material removing tool (which has been used to form a recess) must be followed by a treatment with a second tool which cuts a thread into the surface surrounding the recess. An internal thread is necessary if the recess is to receive a portion of an externally threaded shank forming part of a screw, bolt, spindle, feed screw, pin, post or the like. For example, it is often necessary to accurately center the workpiece relative to another part by resorting to so-called alignment, locating or centering pins (also called fixing or stead pins), dowel pins, drift pins or plugs, set pins or the like. A centering pin must be installed in a recess with a very high degree of accuracy in order to ensure that the thus coupled and centered parts are secured to each other with a minimum of play, i.e., within an acceptable range of tolerances. Such accuracy can be achieved by resorting to material removing and surface smoothing tools in the form of reamers or the like. All this contributes significantly to the cost of the workpieces, of the combinations of such workpieces with one or more additional workpieces as well as of the machines, apparatus or other devices in which the recessed workpieces are put to use. In addition, it is often difficult to dismantle an apparatus, machine or another device which employs one or more workpieces having one or more recesses which are obtained as a result of removal of metallic material from a blank or from a semifinished component of a friction clutch or the like.
An object of the invention is to provide a method of making recesses (such as tapped or untapped blind holes or through holes) in metallic workpieces in a simple and inexpensive manner.
Another object of the invention is to provide a method which renders it possible to avoid removal of material from a workpiece in the course of a recess forming or making operation.
A further object of the invention is to provide a method which can be utilized for the making of recesses in workpieces including or constituting blanks or preforms of sheet metal.
An additional object of the invention is to provide a method which renders it possible to make recesses with a high degree of accuracy so that the recesses can accept centering pins, other types of pins, screws, bolts or other male parts with a minimum of play or with no play at all.
Still another object of the invention is to provide a method of making recesses in the end faces of relatively thin workpieces in the form of cylinders, tubes, pipes, sheets or panels in such a way that the diameter or another maximum transverse dimension of a recess at least matches but can exceed the wall thickness of the workpiece.
A further object of the invention is to provide a novel and improved method of treating blanks which can be utilized for the making of covers or housings of friction clutches for use in motor vehicles.
Another object of the invention is to provide a method which can be resorted to for accurately assembling component parts of covers or housings for use in torque transmitting apparatus, such as friction clutches in motor vehicles.
further object of the invention is to provide a method of making recesses which can be practiced by resorting to simple and readily available tools, implements and apparatus.
An additional object of the invention is to provide a torque transmitting apparatus at least one component of which has been treated in accordance with the above outlined method and which can be readily assembled or partially or fully dismantled in a time saving manner.
Another object of the invention is to provide a relatively complex aggregate which can be readily assembled or dismantled because one or more of its components were treated in accordance with the above outlined method.
Still another object of the invention is to provide a torque transmitting apparatus which employs a composite flywheel assembly and a friction clutch utilizing at least one component which has been treated in accordance with the above outlined method.
A further object of the invention is to provide a torque transmitting apparatus at least certain parts of which can be produced, finished, assembled and/or otherwise processed with substantial savings in energy and which is constructed and assembled in such a way that at least a majority of its constituents can be readily separated from each other for inspection, repair or replacement so that each set of parts consisting of the same material can be recycled in an ecologically acceptable manner.
Another object of the invention is to provide a torque transmitting apparatus which can be assembled, inspected, repaired and/or dismantled with greater facility and at a lower cost than heretofore known torque transmitting apparatus.
An additional object of the invention is to provide a torque transmitting apparatus which can be assembled with considerable savings in primary energy and with minimal waste in metallic material.
Still another object of the invention is to provide a method which renders it possible to provide one or more workpieces with tapped or untapped recesses without any contamination of the surrounding area.
A further object of the invention is to provide a method which renders it possible to provide metallic workpieces with recesses free of shavings and/or any other foreign particles necessitating collection and/or expulsion prior to putting the thus treated workpieces to actual use.
Another object of the invention is to provide a method which renders it possible to provide a metallic or partially metallic workpiece with one or more recesses without the need for cooling the workpiece or with minimal cooling.
An additional object of the invention is to provide a method which renders it possible to provide a metallic or at least partially metallic workpiece with one or more recesses without the need for lubrication of tools serving to provide the workpiece with a blind hole, a tapped hole or another recess.
Still another object of the invention is to provide a method which renders it possible to reduce the overall weight of a finished workpiece and which can be practiced in such a way that the tools and/or implements which are used to make one or more recesses can be put to use in, or in conjunction with, the thus treated workpiece.
A further object of the invention is to provide a composite flywheel assembly, particularly for use in torque transmitting apparatus of the type employed in motor vehicles, which is more compact, particularly in the radial direction, than heretofore known flywheel assemblies.
Another object of the invention is to provide a torque transmitting apparatus which is constructed and assembled in such a way that the space heretofore occupied by conventional flywheel assemblies can be put to use to accommodate other components of such apparatus.
An additional object of the invention is to provide a novel and improved cover or housing for connection to the diaphragm spring, damper or dampers, clutch disc, pressure plate and/or other components of a friction clutch for motor vehicles.
One feature of the present invention resides in the provision of a method of making a recess (e.g., a blind hole or a through hole) in a surface of a workpiece containing a metallic material. The improved method comprises the step of driving into the surface of the workpiece a material displacing tool which includes a trailing portion having a larger first cross-sectional area and a front portion or leader having a smaller second cross-sectional area. The driving step includes advancing the tool in the longitudinal direction thereof, namely in a direction from the trailing portion toward the leader so that the leader penetrates a selected portion of the surface of the workpiece and displaces the material of the workpiece at least substantially transversely of the aforementioned direction.
In many instances, the recess will have to be formed in an end surface of a workpiece which has a predetermined length (as measured from the end surface). The advancing step of such method can include moving the tool substantially lengthwise of the workpiece.
If the workpiece has a predetermined minimum wall thickness prior to the tool advancing step and the surface is an end surface of the workpiece, the driving step can include utilizing a tool which is dimensioned to provide the surface of the workpiece with a recess having a maximum transverse dimension at least matching the minimum wall thickness, i.e., the maximum transverse dimension (such as the diameter of a circular recess) can exceed the minimum wall thickness of the workpiece.
The method can further comprise the step of fixedly holding the workpiece adjacent the selected portion of the surface, at least in the course of the advancing step.
If the recess is to be made in an end portion of a tubular workpiece, the aforementioned surface can constitute an end surface of the end portion of such tubular workpiece.
The method can further comprise the step of converting a blank (such as a piece of sheet metal) into the workpiece prior to the driving step, and the converting step can include drawing, forging and/or otherwise shaping the blank. The blank can be converted into a tubular (e.g., an at least substantially cylindrical) workpiece.
The workpiece can have at least one additional surface, and the method can further comprise the step of calibrating, at least in part, the at least one additional surface. For example, the recess might be necessary in an end face of a tubular workpiece further having an internal surface and an external surface; the calibrating step can include calibrating the internal and/or the external surface of such workpiece.
If the workpiece is designed to have an axis of rotation, the direction of advancement of the leader of the tool into a surface of such workpiece can be at least substantially parallel to the axis of rotation.
The method can further comprise the step of leaving at least the leader of the tool in the recess. Alternatively, the method can comprise the additional step of withdrawing the tool from the recess.
The driving step can include employing a tool which imparts to the recess a substantially circular, polygonal, oval or other cross-sectional outline.
The method can comprise the additional step of anchoring an element in the recess. The anchored element can include or constitute a locating or centering pin. Such anchored element can constitute a portion of or the entire material displacing tool, i.e., the tool can be left in the freshly formed recess to constitute an anchoring, locating, centering or like element.
The method can also comprise the additional step of providing the workpiece with an internal thread in the recess. Such additional step can include employing a tapping tool which does not remove shavings from the workpiece, e.g., a so-called thread rolling tool or an analogous tool. The tapping tool can be constituted by the aforediscussed material displacing tool which is used to make the recess.
The method can also include the step of anchoring the workpiece of a male fastener including a first portion in the recess and an externally threaded second portion outside of the recess. Such method can also comprise the step of moving at least one nut into mesh with the externally threaded second portion of the fastener. The anchoring step can include employing a male fastener having an externally threaded first portion in mesh with the workpiece. The male fastener can include or constitute a screw or a bolt. For example, the anchoring step can include employing a male fastener having a first portion which displaces the material of the workpiece during introduction into the workpiece. The method can also comprise the step of withdrawing the material displacing tool from the recess prior to the anchoring step.
At least a portion of the workpiece can consist of sheet metal, and the driving step can include making in the sheet metal a recess in the form of a through hole or a blind hole.
Another feature of the invention resides in the provision of a metallic component which can constitute an element of a friction clutch and has a surface provided with at least one recess which is formed in accordance with the aforediscussed method, i.e., as a result of driving into the surface of the metallic component a material displacing tool (of the type including a trailing portion having a larger first cross-sectional area and a front portion or leader having a smaller second cross-sectional area) in such a way that the leader has penetrated the surface in a direction from the trailing portion toward the leader (which latter can constitute or include a substantially conical or pyramidal tip) and the tool has displaced the material of the metallic component at least substantially transversely of the aforementioned direction from the trailing end toward the leader. The metallic component can include or constitute or form part of a housing or casing. For example, the housing or casing can include a tubular (e.g., at least substantially cylindrical) section having an end portion, and a second section which is separably affixed to the tubular section. The aforementioned recess surface is or can be provided on the tubular section of the housing or casing.
A further feature of the invention resides in the provision of a friction clutch which comprises a composite flywheel assembly connectable to a combustion engine and including a secondary flywheel, and a tubular (e.g., an at least substantially cylindrical) metallic component which is carried by the secondary flywheel and has a surface provided with a plurality of tapped recesses (e.g., in the form of blind holes) which are spaced apart from each other circumferentially of the tubular component. At least one of the recesses is obtained in accordance with the aforediscussed method, i.e., as a result of driving into the surface a material displacing tool, including a trailing portion having a larger first cross-sectional area and a leader or front portion having a smaller second cross-sectional area, in such a way that the leader has penetrated into the surface in a direction from the trailing portion toward the leader and the tool has displaced the material of the metallic component at least substantially transversely of the aforementioned direction. The clutch further comprises a housing or cover section adjacent the surface of the metallic component, and threaded fasteners (e.g., in the form of bolts or screws) which secure the housing or cover section to the metallic component and have portions (e.g., in the form of externally threaded shanks) extending into the recesses. The housing or cover section can extend substantially radially of and can be separably secured to the tubular metallic component. Such friction clutch can further comprise a diaphragm spring or an analogous resilient biasing device which is tiltably carried by the housing or cover section. The secondary flywheel is rotatable about a predetermined axis and the friction clutch can further comprise a pressure plate and means for non-rotatably but axially movably securing the pressure plate to the tubular metallic component for movement in the direction of the axis of the secondary flywheel. Such friction clutch can further comprise energy storing elements which are deformable in the circumferential direction of the composite flywheel. The tubular component of such friction clutch can be provided with means (e.g., in the form of arms) for deforming or stressing the energy storing elements. The energy storing elements can include or constitute elongated arcuate coil springs.
An additional feature of the present invention resides in the provision of a torque transmitting apparatus which comprises a composite housing or cover rotatable about a predetermined axis and including a component extending in the direction of the axis and having a surface provided with at least one recess formed in accordance with the aforediscussed method, i.e., such recess can be obtained as a result of driving into the surface a material displacing tool (including a trailing having a larger first cross-sectional area and a front portion or leader having a smaller second cross-sectional area) in such a way that the leader has penetrated the surface in a second direction from the trailing portion toward the leader and the tool has displaced the material of the component at least substantially transversely of the second direction. The second direction is or can be at least substantially parallel to the direction of extension of the aforementioned component. The housing can constitute a cover of a friction clutch for use in motor vehicles.
An additional feature of the present invention resides in the provision of an apparatus for compensating for torsional stresses. Such apparatus comprises a first flywheel which is connectable with an engine (e.g., with the crankshaft or an analogous output element of the engine in a motor vehicle), and a second flywheel connectable with an input element of a transmission (such as a variable-speed transmission in the power train between the engine and the wheels of a motor vehicle) The flywheels are rotatable relative to each other and the apparatus further comprises at least one damper having means (such as the aforediscussed arcuate coil springs) for yieldably opposing rotation of the flywheels relative to each other. Such apparatus preferably further comprises at least one antifriction bearing which is interposed between the flywheels, and a metallic component which is affixed to one of the flywheels (particularly to the second flywheel) and extends in the direction of the axis of rotation of the one flywheel. The component has a surface provided with at least one recess formed in accordance with the aforediscussed method, namely as a result of driving into the surface a material displacing tool (including a trailing portion having a larger first cross-sectional area and a front portion or leader having a smaller second cross-sectional area) in such a way that the leader has penetrated the surface in a second direction from the trailing portion toward the leader and the tool has thereby displaced the material of the component at least substantially transversely of the second direction. The apparatus further comprises a housing portion or cover portion which is connectable to the aforediscussed component, e.g., by fasteners one of which extends into the aforediscussed recess. The apparatus of the just outlined character can further comprise means (e.g., bolts or analogous threaded fasteners) for affixing one of the flywheels (normally the first flywheel) to an output element of a combustion engine.
Still another feature of the invention resides in the provision of a friction clutch which comprises a housing or cover made at least in part of sheet metal and including an at least substantially cylindrical first-section having an axial end and a second section disposed at the axial end and extending at least substantially radially of the first section, threaded fasteners which separably connect the two sections to each other, a pressure plate which is non-rotatably affixed to the housing or cover for movement in the axial directions of the first section, and means (e.g., including a diaphragm spring) for biasing the pressure plate axially of the first section. The axial end of the first section preferably includes a surface which is provided with recesses extending substantially axially of the first section and formed in accordance with the aforediscussed method, namely as a result of driving into the surface a material displacing tool which has displaced the material of the first section substantially radially of the respective recess.
An additional feature of the invention resides in the provision of a friction clutch comprising a component (such as a cover or housing) including a substantially cylindrical section, a composite flywheel assembly including a flywheel connectable with an output element of a combustion engine, energy storing elements acting in the circumferential direction of and reacting against the flywheel assembly, and torque transmitting elements provided on the substantially cylindrical section and bearing against the energy storing elements. The aforementioned component can comprise a second section which is separably affixed to the substantially cylindrical section. The latter consists of or can consist, at least in part, of a metallic sheet material. The substantially cylindrical section preferably includes a surface which is adjacent the second section and is provided with recesses at least one of which is obtained as a result of displacing the material of the substantially cylindrical section substantially radially of the axis of the at least one recess, preferably entirely without removal of shavings and/or otherwise configurated pieces of the substantially cylindrical section.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved method itself, however, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings.